Some studies have supported the use of St John's wort preparations as a treatment for depression in humans.[5][6] In contrast, the National Center for Complementary and Integrative Medicine of the United States National Institutes of health warns that St. John's wort is not a proven treatment for depression, that it has many drug-drug interactions that can reduce the effectiveness of other medications, and that psychosis can occur as a rare side effect.[7] The FDA has also warned of the potential of St. John's wort to reduce the effectiveness of other medications.[8]

Hypericum perforatum is a yellow-flowering, stoloniferous or sarmentose, perennialherb indigenous to Europe. It has been introduced to many temperate areas of the world and grows wild in many meadows. The herb's common name comes from its traditional flowering and harvesting on St John's day, 24 June. The genus name Hypericum is derived from the Greek words hyper (above) and eikon (picture), in reference to the plant's traditional use in warding off evil by hanging plants over a religious icon in the house during St John's day. The species name perforatum refers to the presence of small oil glands in the leaves that look like windows, which can be seen when they are held against the light.[2]

St John's wort is a perennial plant with extensive, creeping rhizomes. Its stems are erect, branched in the upper section, and can grow to 1 m high. It has opposing, stalkless, narrow, oblong leaves that are 12 mm long or slightly larger. The leaves are yellow-green in color, with transparent dots throughout the tissue and occasionally with a few black dots on the lower surface.[2] Leaves exhibit obvious translucent dots when held up to the light, giving them a ‘perforated’ appearance, hence the plant's Latin name.

Its flowers measure up to 2.5 cm across, have five petals, and are colored bright yellow with conspicuous black dots. The flowers appear in broad cymes at the ends of the upper branches, between late spring and early to mid summer. The sepals are pointed, with glandular dots in the tissue. There are many stamens, which are united at the base into three bundles. The pollen grains are ellipsoidal.[2]

When flower buds (not the flowers themselves) or seed pods are crushed, a reddish/purple liquid is produced.

St John's wort reproduces both vegetatively and sexually. It thrives in areas with either a winter- or summer-dominant rainfall pattern; however, distribution is restricted by temperatures too low for seed germination or seedling survival. Altitudes greater than 1500 m, rainfall less than 500 mm, and a daily mean January (in Southern hemisphere) temperature greater than 24 degrees C are considered limiting thresholds. Depending on environmental and climatic conditions, and rosette age, St John's wort will alter growth form and habit to promote survival. Summer rains are particularly effective in allowing the plant to grow vegetatively, following defoliation by insects or grazing.

The seeds can persist for decades in the soil seed bank, germinating following disturbance.[9]

In large doses, St John's wort is poisonous to grazing livestock (cattle, sheep, goats, horses).[10] Behavioural signs of poisoning are general restlessness and skin irritation. Restlessness is often indicated by pawing of the ground, headshaking, head rubbing, and occasional hindlimb weakness with knuckling over, panting, confusion, and depression. Mania and hyperactivity may also result, including running in circles until exhausted. Observations of thick wort infestations by Australian graziers include the appearance of circular patches giving hillsides a ‘crop circle’ appearance, it is presumed, from this phenomenon. Animals typically seek shade and have reduced appetite. Hypersensitivity to water has been noted, and convulsions may occur following a knock to the head. Although general aversion to water is noted, some may seek water for relief.

Severe skin irritation is physically apparent, with reddening of non-pigmented and unprotected areas. This subsequently leads to itch and rubbing, followed by further inflammation, exudation, and scab formation. Lesions and inflammation that occur are said to resemble the conditions seen in foot and mouth disease. Sheep have been observed to have face swelling, dermatitis, and wool falling off due to rubbing. Lactating animals may cease or have reduced milk production; pregnant animals may abort. Lesions on udders are often apparent. Horses may show signs of anorexia, depression (with a comatose state), dilated pupils, and injected conjunctiva.

Increased respiration and heart rate is typically observed while one of the early signs of St John's wort poisoning is an abnormal increase in body temperature. Affected animals will lose weight, or fail to gain weight; young animals are more affected than old animals. In severe cases death may occur, as a direct result of starvation, or because of secondary disease or septicaemia of lesions. Some affected animals may accidentally drown. Poor performance of suckling lambs (pigmented and non-pigmented) has been noted, suggesting a reduction in the milk production, or the transmission of a toxin in the milk.

secondary photosensitisation from plant-associated damage to the liver.

Araya and Ford (1981) explored changes in liver function and concluded there was no evidence of Hypericum-related effect on the excretory capacity of the liver, or any interference was minimal and temporary. However, evidence of liver damage in blood plasma has been found at high and long rates of dosage.

Photosensitisation causes skin inflammation by a mechanism involving a pigment or photodynamic compound, which when activated by a certain wavelength of light leads to oxidation reactions in vivo. This leads to lesions of tissue, particularly noticeable on and around parts of skin exposed to light. Lightly covered or poorly pigmented areas are most conspicuous. Removal of affected animals from sunlight results in reduced symptoms of poisoning.

St John's wort is widely known as a herbal treatment for depression. In some countries, such as Germany, it is commonly prescribed for mild to moderate depression, especially in children and adolescents.[12] Specifically, Germany has a governmental organization called Commission E which regularly performs rigorous studies on herbal medicine. It is proposed that the mechanism of action of St. John's wort is due to the inhibition of reuptake of certain neurotransmitters.[2] The best studied chemical components of the plant are hypericin and pseudohypericin.

An analysis of twenty-nine clinical trials with more than five thousand patients was conducted by Cochrane Collaboration. The review concluded that extracts of St John's wort were superior to placebo in patients with major depression. St John's wort had similar efficacy to standard antidepressants. The rate of side-effects was half that of newer SSRI antidepressants and one-fifth that of older tricyclic antidepressants.[13] A report[13] from the Cochrane Review states:

The available evidence suggests that the Hypericum extracts tested in the included trials a) are superior to placebo in patients with major depression; b) are similarly effective as standard antidepressants; and c) have fewer side-effects than standard antidepressants.

In contrast, the National Center for Complementary and Integrative Health of the United States National Institutes of health warns that St. John's wort is not a proven treatment for depression, that it has many drug-drug interactions that can reduce the effectiveness of other medications, and that psychosis can occur as a rare side effect.[7] The FDA has also warned of the potential of St. John's wort to reduce the effectiveness of other medications.[8]

St John's wort is being studied for effectiveness in the treatment of certain somatoform disorders. Results from the initial studies are mixed and still inconclusive; some research has found no effectiveness, other research has found a slight lightening of symptoms. Further study is needed and is being performed.

A major constituent chemical, hyperforin, may be useful for treatment of alcoholism, although dosage, safety and efficacy have not been studied.[14][15] Hyperforin has also displayed antibacterial properties against Gram-positive bacteria, although dosage, safety and efficacy has not been studied.[16]Herbal medicine has also employed lipophilic extracts from St John's wort as a topical remedy for wounds, abrasions, burns, and muscle pain.[15] The positive effects that have been observed are generally attributed to hyperforin due to its possible antibacterial and anti-inflammatory effects.[15] For this reason hyperforin may be useful in the treatment of infected wounds and inflammatory skin diseases.[15] In response to hyperforin's incorporation into a new bath oil, a study to assess potential skin irritation was conducted which found good skin tolerance of St John's wort.[15]

A randomized controlled trial of St John's wort found no significant difference between it and placebo in the management of ADHD symptoms over eight weeks. However, the St John's wort extract used in the study, originally confirmed to contain 0.3% hypericin, was allowed to degrade to levels of 0.13% hypericin and 0.14% hyperforin. Given that the level of hyperforin was not ascertained at the beginning of the study, and levels of both hyperforin and hypericin were well below that used in other studies, little can be determined based on this study alone.[17] Hypericin and pseudohypericin have shown both antiviral and antibacterial activities. It is believed that these molecules bind non-specifically to viral and cellular membranes and can result in photo-oxidation of the pathogens to kill them.[2]

A research team from the Universidad Complutense de Madrid (UCM) published a study entitled "Hypericum perforatum. Possible option against Parkinson's disease", which suggests that St John's wort has antioxidant active ingredients that could help reduce the neuronal degeneration caused by the disease.[18][19][20][21]

Recent evidence suggests that daily treatment with St John's wort may improve the most common physical and behavioural symptoms associated with premenstrual syndrome.[22]

St John's wort is generally well tolerated, with an adverse effect profile similar to placebo.[25] The most common adverse effects reported are gastrointestinal symptoms, dizziness, confusion, tiredness and sedation.[26][27] It also decreases the levels of estrogens, such as estradiol, by speeding up its metabolism, and should not be taken by women on contraceptive pills as it upregulates the CYP3A4 cytochrome of the P450 system in the liver.[28]

St John's wort may rarely cause photosensitivity. This can lead to visual sensitivity to light and to sunburns in situations that would not normally cause them.[25] Related to this, recent studies concluded that the extract reacts with light, both visible and ultraviolet, to produce free radicals, molecules that can damage the cells of the body. These can react with vital proteins in the eye that, if damaged, precipitate out, causing cataracts.[29] Another study found that in low concentrations, St. John's wort inhibits free radical production in both cell-free and human vascular tissue, revealing antioxidant properties of the compound. The same study found pro-oxidant activity at the highest concentration tested.[30]

Consumption of St. John's wort is discouraged for those with bipolar disorder. There is concern that people with bipolar depression taking St. John’s wort may be at a higher risk for mania.[32]

While St. John's wort shows some promise in treating children, it is advised that it be only done with medical supervision. [32]

The interactions that St. John's Wort has with other medications is also well studied and has yielded significant results of drug interactions with medications such as Selective Serotonin Re-uptake Inhibitor (SSRI) antidepressants, warfarin, and birthcontrol. Combining both SJW and SSRI depressants can lead to increased serotonin levels causing a potentially fatal serotonin syndrome.[33] SJW will reduce the effects of warfarin and lead to thrombosis.[34] Combining estrogen containing oral contraceptives with SJW can lead to decreased efficacy of the contraceptive and eventually unplanned pregnancies.[35] These are just a few of the drug interactions that SJW possesses. It is also known to decrease the efficacy of HIV medications, Cholesterol medications, as well as transplant medications.[36] It should be noted, however, that traditional SSRI antidepressants such as Fluvoxamine carry similar contraindications, due to the inhibition of liver enzymes in the same way as St. John's Wort.

St John's wort has been shown to cause multiple drug interactions through induction of the cytochrome P450 enzymes CYP3A4 and CYP2C9, and CYP1A2 (females only). This drug-metabolizing enzyme induction results in the increased metabolism of certain drugs, leading to decreased plasma concentration and potential clinical effect.[37] The principal constituents thought to be responsible are hyperforin and amentoflavone.

St John's wort has also been shown to cause drug interactions through the induction of the P-glycoprotein (P-gp) efflux transporter. Increased P-gp expression results in decreased absorption and increased clearance of certain drugs, leading to lower plasma concentration and potential clinical efficacy.[38]

Examples of drugs whose effectiveness may be reduced by St. John's wort

Hypericin, pseudohypericin, and hyperforin may be quantitated in plasma as confirmation of usage and to estimate the dosage. These three active substituents have plasma elimination half-lives within a range of 15–60 hours in humans. None of the three has been detected in urine specimens.[40]

The naphthodianthrones hypericin and pseudohypericin along with the phloroglucinol derivative hyperforin are thought to be among the numerous active constituents.[2][43][44][45] It also contains essential oils composed mainly of sesquiterpenes.[2]

Inhibits the following: inflammation (via NF-κB and STAT1 inhibition),[86] cancer, HDAC,[87] bacteria, viruses, protozoa and fungi.[88] It is also known to prevent cardiovascular disease and cancer.[88]

Partition coefficient. These values are experimental values taken from ChemSpider and [100] (the access dates are both 13–15 December 2013) where available or, if they are not available approximations are taken from [www.chemaxon.com/download/marvin/for-end-users/ ChemAxon MarvinSketch] 6.1.4 & [101]

^Values given in brackets are IC50/EC50 depending on whether it's an inhibitory or inductive action the compound displays towards the biologic target in question. If it pertains to bacterial growth inhibition the value is MIC50

^"Enzymes". Hyperforin. Human Metabolome Database. 3.6. University of Alberta. 30 June 2013. Retrieved 12 December 2014. Hyperforin is found in alcoholic beverages. Hyperforin is a constituent of Hypericum perforatum (St John's Wort) Hyperforin is a phytochemical produced by some of the members of the plant genus Hypericum, notably Hypericum perforatum (St John's wort). The structure of hyperforin was elucidated by a research group from the Shemyakin Institute of Bio-organic Chemistry (USSR Academy of Sciences in Moscow) and published in 1975. Hyperforin is a prenylated phloroglucinol derivative. Total synthesis of hyperforin has not yet been accomplished, despite attempts by several research groups. Hyperforin has been shown to exhibit anti-inflammatory, anti-tumor, antibiotic and anti-depressant functions (PMID 17696442 , 21751836 , 12725578 , 12018529 )1. Arachidonate 5-lipoxygenase ...Specific function: Catalyzes the first step in leukotriene biosynthesis, and thereby plays a role in inflammatory processes ...2. Prostaglandin G/H synthase 1 ... General function: Involved in peroxidase activity

^Wölfle U, Seelinger G, Schempp CM (2014). "Topical application of St. John's wort (Hypericum perforatum)". Planta Med.80 (2-3): 109–20. doi:10.1055/s-0033-1351019. PMID24214835. Anti-inflammatory mechanisms of hyperforin have been described as inhibition of cyclooxygenase-1 (but not COX-2) and 5-lipoxygenase at low concentrations of 0.3 µmol/L and 1.2 µmol/L, respectively [52], and of PGE2 production in vitro [53] and in vivo with superior efficiency (ED50 = 1 mg/kg) compared to indomethacin (5 mg/kg) [54]. Hyperforin turned out to be a novel type of 5-lipoxygenase inhibitor with high effectivity in vivo [55] and suppressed oxidative bursts in polymorphonuclear cells at 1.8 µmol/L in vitro [56]. Inhibition of IFN-γ production, strong downregulation of CXCR3 expression on activated T cells, and downregulation of matrix metalloproteinase 9 expression caused Cabrelle et al. [57] to test the effectivity of hyperforin in a rat model of experimental allergic encephalomyelitis (EAE). Hyperforin attenuated the symptoms significantly, and the authors discussed hyperforin as a putative therapeutic molecule for the treatment of autoimmune inflammatory diseases sustained by Th1 cells.Vancouver style error (help)